1. Field of the Invention
The invention relates to an optical touch device and a method for detecting touch point and, more particularly, to an optical touch device and a method for detecting touch point capable of determining the number of touch points accurately.
2. Description of the Prior Art
Since consumer electronic products have become more and more lighter, thinner, shorter, and smaller, there is no space on these products for containing a conventional input device, such as mouse, keyboard, etc. With development of touch technology, in various kinds of consumer electronic products (e.g. display device, all-in-one device, mobile phone, personal digital assistant (PDA), etc.), a touch device has become a main tool for data input. Compared with other touch design, such as a resistive touch design, a capacitive touch design, an ultrasonic touch design, or a projective touch design, an optical touch design has lower cost and is easier to use, especially for large-size touch display.
A conventional optical touch device senses a touch point indicated by a touch object (e.g. finger or stylus) on an indication plane by two image sensing units arranged oppositely. When the image sensing units sense the touch object on the indication plane, a processing unit of the optical touch device can calculate the touch point indicated by the touch object accordingly. When the conventional optical touch device is used for sensing one single touch point performed by one single finger, the position of the touch point can be calculated by a triangulation method easily. However, once there are multiple touch points performed by two or more than two fingers, it is complicated to identify and calculate the number of touch points and this could result in mis-identification and interference.